Flexible display and method for manufacturing the same

ABSTRACT

A flexible display comprises a flexible substrate made of plastic material, a display element on a first surface of the flexible substrate, and a surface residual film containing at least one of a metal material or a metal oxide material. The surface residual film is bonded to at least a part of a second surface of the flexible substrate. The second surface is opposed to the first surface. A method for manufacturing a flexible display comprises preparing a glass substrate, forming adhesive material film on the glass substrate, the adhesive material film being made of at least one of a metal material or a metal oxide material, and forming a flexible substrate from plastic material on the adhesive material film.

BACKGROUND

1. Field

The embodiments relate to a flexible display and a method formanufacturing the same. More particularly, the embodiments relate to aflexible display which can be stably formed and a method formanufacturing the same.

2. Description of the Related Art

In recent years, flexible displays having a lightweight andshock-resistant flexible substrate made of materials such as plasticshave been developed. Portability of such flexible displays can bemaximized since they can be folded or rolled up. Also, such flexibledisplays can be applied in various fields.

A flexible display includes a display element formed on a flexiblesubstrate. Different types of display elements may be used in a flexibledisplay, including an organic light emitting diode display device, aliquid crystal display device, and an electrophoretic display (EPD)device, etc.

These types of display elements commonly include thin film transistors.Accordingly, in order to form a flexible display, the flexible substrateundergoes a number of thin film processes to form thin film transistors.

Since the flexible substrate generally has a relatively thin thicknessof several tens of micrometers, it was difficult to perform a number ofthin film processes separately on the flexible substrate. Currently, amethod in which a flexible substrate is firstly formed on a glasssubstrate, a display element is formed on the flexible substrate adheredto the glass substrate, and then the flexible substrate and the glasssubstrate are separated from each other is used to perform thin filmprocesses.

A flexible substrate made of plastic material generally has acoefficient of thermal expansion (CTE) that is different from the CTE ofthe glass substrate. If the adhesion force between the flexiblesubstrate and the glass substrate is weak, then the flexible substratemay peel off and away from the glass substrate or be partly removed andbent during a high-temperature process. This may cause a fatal defect inthe manufacturing process of a flexible display.

The above described information is only for enhancement of understandingof the background of the described technology. Therefore, it may containinformation that does not form the prior art that is already known inthis country to a person of ordinary skill in the art.

SUMMARY

Embodiments are therefore directed to a flexible display, which can bestably formed, and a method for manufacturing the same, whichsubstantially overcome one or more of the problems due to thelimitations and disadvantages of the related art.

It is therefore a feature of an embodiment to provide a flexibledisplay, comprising a flexible substrate made of plastic material, adisplay element on a first surface of the flexible substrate, and asurface residual film containing at least one of a metal material or ametal oxide material, the surface residual film being bonded to at leasta part of a second surface of the flexible substrate, the second surfaceof the flexible substrate being opposed to the first surface.

The plastic material may include a functional group of —CONH—.

The flexible substrate may be formed from a material containing apolyimide.

The flexible substrate may have a thickness ranging from 5 μm to 200 μm.

The flexible substrate may have a coefficient of thermal expansionranging from 3 ppm/° C. to 10 ppm/° C.

The surface residual film may contain a material bonded to thefunctional group of —CONH—.

The metal material may be bonded to the functional group of —CONH—, andthe metal material may include at least one of aluminum, gallium,indium, titanium, molybdenum, and zinc.

The metal oxide material may be bonded to the functional group of—CONH—, and the metal oxide material may include at least one ofaluminum oxide, gallium oxide, zinc oxide, titanium oxide, indium oxide,indium tin oxide, indium zinc oxide, and gallium indium zinc oxide.

The display element may include a thin film transistor.

The display element may be an organic light emitting diode displaydevice, a liquid crystal display device, or an electrophoretic displaydevice.

The surface residual film may have a thickness ranging from 0.1 nm to1000 nm.

It is therefore another feature of an embodiment to provide a method formanufacturing a flexible display, comprising: preparing a glasssubstrate; forming adhesive material film on the glass substrate, theadhesive material film being made of at least one of metal material andmetal oxide material; and forming a flexible substrate from plasticmaterial on the adhesive material film.

The plastic material may include a functional group of —CONH—.

The flexible substrate may be formed from material containing polyimide.

The flexible substrate may be formed by a slit coating method or ascreen printing method.

The flexible substrate has a thickness ranging from 5 μm to 200 μm.

The flexible substrate may have the same coefficient of thermalexpansion as the glass substrate.

The flexible substrate may have a coefficient of thermal expansion ofless than 10 ppm/° C.

The adhesive material film may contain material capable of being bondedto the functional group of —CONH—.

The metal material may be bonded to the functional group of —CONH—, andthe metal material may include at least one of aluminum, gallium,indium, titanium, molybdenum, and zinc.

The metal oxide material may be bonded to the functional group of—CONH—, and the metal oxide material may include at least one ofaluminum oxide, gallium oxide, zinc oxide, titanium oxide, indium oxide,indium tin oxide, indium zinc oxide, and gallium indium zinc oxide.

The adhesive material film may be formed by atomic layer deposition.

The adhesive material film may have a thickness ranging from 0.1 nm to1000 nm.

The method may further comprise separating the flexible substrate andthe glass substrate from each other.

The flexible substrate and the adhesive material film may be separatedfrom each other by radiation of laser light.

The adhesive material film and the glass substrate may be separated fromeach other by radiation of laser light.

The method may further comprise forming a display element on theflexible substrate.

The display element may include a thin film transistor.

The display element may be any one of an organic light emitting diodedisplay device, a liquid crystal display device, and an electrophoreticdisplay device.

According to embodiments, the flexible display may effectively suppressoccurrence of a defect.

Furthermore, the method for manufacturing a flexible display accordingto embodiments can stably manufacture the above-described flexibledisplay by effectively improving bonding force between the flexiblesubstrate and the glass substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages will become more apparent tothose of ordinary skill in the art by describing in detail exemplaryembodiments with reference to the attached drawings, in which:

FIG. 1 illustrates a cross-sectional view of a flexible displayaccording to an exemplary embodiment;

FIG. 2 illustrates an enlarged layout view of pixels in the flexibledisplay illustrated in FIG. 1;

FIG. 3 illustrates a cross-sectional view of a pixel along lineillustrated in FIG. 2; and

FIGS. 4-7 illustrate cross-sectional views of the flexible displayillustrated in FIG. 1 in sequential manufacturing processes.

DETAILED DESCRIPTION

Korean Patent Application No. 10-2009-0080769, filed on Aug. 28, 2009,in the Korean Intellectual Property Office, and entitled: “FlexibleDisplay and Method for Manufacturing the Same,” is incorporated byreference herein in its entirety.

Example embodiments will now be described more fully hereinafter withreference to the accompanying drawings; however, they may be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art.

In the drawing figures, the dimensions of layers and regions may beexaggerated for clarity of illustration. It will also be understood thatwhen a layer or element is referred to as being “on” another layer orsubstrate, it can be directly on the other layer or substrate, orintervening layers may also be present. In addition, it will also beunderstood that when a layer is referred to as being “between” twolayers, it can be the only layer between the two layers, or one or moreintervening layers may also be present. Like reference numerals refer tolike elements throughout.

Hereinafter, an exemplary embodiment will be described with reference toFIG. 1.

A flexible display 101 may include a flexible substrate 111, a displayelement 110 formed on a first surface of the flexible substrate 111, anda surface residual film 119 bonded to at least a part of a secondsurface of the flexible substrate 111. As used herein, the secondsurface of the flexible substrate 111 refers to the surface on the otherside or opposite side of the flexible substrate relative to the firstsurface on which the display element 110 is formed.

The flexible substrate 111 may be made of plastic material.Specifically, the flexible substrate 111 may be made of plastic materialcontaining a functional group of —CONH—. For example, the plasticmaterial may be a polyimide containing the functional group of —CONH—.Polyimides exhibit excellent heat resistance characteristics, and sincethe flexible display 101 undergoes a high-temperature process,polyimides are highly suitable as a raw material in making the flexiblesubstrate 111.

The flexible substrate 111 may have a thickness ranging from 5 μm to 200μm. If the flexible substrate 111 has a thickness of less than 5 μm, itmay be difficult for the flexible substrate 111 to stably support thedisplay element 110. Moreover, it may be difficult to form the flexiblesubstrate 111 to have a thickness less than 5 μm. On the other hand, ifthe flexible substrate 111 has a thickness greater than 200 μm, theoverall thickness of the flexible display device 101 may be too large,and its flexibility characteristics may be deteriorated.

The flexible substrate 111 may be formed to have a CTE ranging from 3ppm/° C. to 10 ppm/° C. If the CTE of the flexible substrate 111 is lessthan 3 ppm/° C. or greater than 10 ppm/° C., a difference in a CTEbetween a glass substrate 900 (shown in FIGS. 4 to 7) and the flexiblesubstrate 111 may be too large. It is important that the flexiblesubstrate 111 and the glass substrate 900 be stably bonded to eachother. However, because of such a large difference in CTE between theflexible substrate 111 and the glass substrate 900, the flexiblesubstrate 111 may peel off and away from the glass substrate 900 duringa high-temperature process, and a fatal defect may be caused.

In accordance with embodiments, a surface residual film 119 may bebonded to the functional group of —CONH— contained in the flexiblesubstrate 111. The surface residual film 119 may contain at least one ofa metal material or a metal oxide material. That is, the at least onemetal material or metal oxide material contained in the surface residualfilm 119 may be bonded to the functional group of —CONH— contained inthe flexible substrate 111.

The metal material may include at least one of aluminum (Al), gallium(Ga), indium (In), titanium (Ti), molybdenum (Mo), and zinc (Zn).

The metal oxide material may include at least one of aluminum oxide,gallium oxide, zinc oxide, titanium oxide, indium oxide, indium tinoxide (ITO), indium zinc oxide (IZO), and gallium indium zinc oxide(GIZO).

The at least one metal material or metal oxide material contained in thesurface residual film 119 may serve to improve bonding force between theflexible substrate 111 and the glass substrate 900 in the manufacturingprocess of the flexible display 101. That is, the at least one metalmaterial or metal oxide material contained in the surface residual film119 may be firmly bonded to the flexible substrate 111. Such firmbonding may effectively suppress or prevent the flexible substrate 111from peeling off or away from the glass substrate 900.

After the display element 110 is formed on the flexible substrate 111,the flexible substrate 111 and the glass substrate 900 may be separatedfrom each other. At this point, at least a part of the metal material ormetal oxide material contained in the surface residual film 119 betweenthe flexible substrate 111 and the glass substrate 900 may be bonded toboth of the flexible substrate 111 and the glass substrate 900.Accordingly, this part of the metal material or metal oxide materialcontained in the surface residual film 119 may remain between theflexible substrate 111 and the glass substrate 900.

The display element 110 may be any one of an organic light emittingdiode display device, a liquid crystal display device, and an EPDdevice. These display elements commonly include thin film transistors(TFTs). Thus, in order to manufacture the flexible display 101, a numberof thin film processes have to be carried out.

FIG. 1 illustrates a flexible display 101 that uses an organic lightemitting diode display device as the display element 110. However,embodiments are not limited to this embodiment.

Hereinafter, the overall configuration of the flexible display 101 willbe described in detail by referring to the flexible display 101 using anorganic light emitting diode display device as the display element 110.

The display element 110 may include an organic light emitting diode 70and a driving circuit DC. The driving circuit DC may include TFTs 10 and20 (shown in FIG. 2). The driving circuit DC may be configured to drivethe organic light emitting diode 70. That is, the organic light emittingdiode 70 may emit light in response to a driving signal transmitted fromthe driving circuit DC to display an image.

An exemplary configuration of the driving circuit DC and the organiclight emitting diode 70 are illustrated in FIGS. 2 and 3. However,embodiments are not limited to the configurations illustrated in FIGS. 2and 3. Various configurations of the driving circuit DC and the organiclight emitting diode 70 may be formed, and modifications to theseconfigurations are within the purview of those of ordinary skill in theart.

Hereinafter, referring to FIGS. 2 and 3, an internal configuration ofthe flexible display 101 having the organic light emitting diode 70 willbe described in detail. FIG. 2 illustrates a layout view of pixels inthe flexible display. FIG. 3 illustrates a cross-sectional view of apixel along line shown in FIG. 2.

FIGS. 2 and 3 illustrate an active matrix (AM)-type organic lightemitting diode display 101 having a 2Tr-1Cap structure in which eachpixel includes two TFTs 10 and 20 and one capacitor 80. However,embodiments are not limited this embodiment. The flexible display 101may be configured so that each pixel includes three or more TFTs and twoor more capacitors. Also, the flexible display 101 may have variousconfigurations by forming additional wiring. Here, a pixel refers to thesmallest unit that is configured to display an image, and is disposed ineach pixel area. The flexible display 101 displays an image through aplurality of pixels.

As illustrated in FIG. 2 and FIG. 3, each pixel of the display element110 may include a switching TFT 10, a driving TFT 20, a capacitor 80,and an organic light emitting diode 70. Here, a component including theswitching TFT 10, the driving TFT 20, and the capacitor 80 is referredto as the driving circuit DC. The display element 110 may furtherinclude a gate line 151 arranged along one direction, a data line 171crossing the gate line 151, and a common power line 172. The data line171 is insulated from the gate line 151.

One pixel may be defined by the gate line 151, the data line 171, andthe common line 172. However, embodiments are not limited to thisembodiment.

The organic light emitting diode 70 may include a first electrode 710serving as an anode, a second electrode 730 serving as a cathode, and anorganic emission layer 720 disposed between the first electrode 710 andthe second electrode 730. However, embodiments are not limited to thisembodiment. Accordingly, the first electrode 710 may be a cathodeelectrode, and the second electrode 730 may be an anode electrode.

The flexible display 101 may be one of front, rear, and dual displaytypes. If the flexible display 101 is of a front display type, the firstelectrode 710 may be formed from a reflective layer, and the secondelectrode 730 may be formed from a semi-transmissive layer. On the otherhand, if the flexible display 101 is of a rear display type, the firstelectrode 710 may be formed from a semi-transmissive layer, and thesecond electrode 730 may be formed from a reflective layer. If theflexible display 101 is of a dual display type, the first electrode 710and the second electrode 730 may be formed from a transparent layer or asemi-transmissive layer.

The reflective layer and the semi-transmissive layer may be made of atleast one metal of magnesium (Mg), silver (Ag), gold (Au), calcium (Ca),lithium (Li), chromium (Cr), and aluminum, or an alloy thereof. It maybe determined whether the first electrode 710 and the second electrode730 are formed from the reflective layer or the semi-transmissive layeraccording to the thickness. In general, the semi-transmissive layer hasa thickness of less than 200 nm. As the semi-transmissive layer becomesthinner, the level of transmittance of light through thesemi-transmissive layer becomes higher. As the semi-transmissive layerbecomes thicker, the level of transmittance of light through thesemi-transmissive layer becomes lower.

The transparent layer may be made of indium tin oxide, indium zincoxide, zinc oxide (ZnO), or indium oxide (In₂O₃).

In addition, the organic emission layer 720 may be formed from multiplelayers including one or more of an emission layer, a hole injectionlayer (HIL), a hole transport layer (HTL), an electron transport layer(ETL), and an electron injection layer (EIL). If the organic emissionlayer 720 includes all of these layers, the hole injection layer may bedisposed on the first electrode 710 serving as an anode, and then thehole transport layer, the emission layer, the electron transport layer,and the electron injection layer may be sequentially stacked on the holeinjection layer. Further, the organic emission layer 720 may furtherinclude another layer, if necessary.

In this manner, the organic light emitting diode 70 may have holes andelectrons injected into the organic emission layer 720 through the firstelectrode 710 and the second electrode 730, respectively. When excitonsformed by recombination of the injected holes and electrons drop from anexcited state to a ground state, the organic light emitting diode 70 mayemit light.

The capacitor 80 may include a pair of capacitor plates 158 and 178between which insulating layer 160 is interposed as an interlayer. Here,the insulating layer 160 is made of a dielectric material. Storagecapacity is determined by electric charges stored in the capacitor 80and a voltage potential difference between the capacitor plates 158 and178.

The switching TFT 10 may include a switching semiconductor layer 131, aswitching gate electrode 152, a switching source electrode 173, and aswitching drain electrode 174. The driving TFT 20 may include a drivingsemiconductor layer 132, a driving gate electrode 155, a driving sourceelectrode 176, and a drain electrode 177.

The switching TFT 10 may be used as a switching element to select apixel to emit light. The switching gate electrode 152 is connected tothe gate line 151. The switching source electrode 173 is connected tothe data line 171. The switching drain electrode 174 may be spaced apartfrom the switching source electrode 173 and connected to one of thecapacitor plates 158.

The driving TFT 20 may apply driving power to the pixel electrode 710 toemit light from the organic emission layer 720 of the organic lightemitting diode 70 in a selected pixel. The driving gate electrode 155may be connected to the capacitor plate 158 connected to the switchingdrain electrode 174. The driving source electrode 176 and the othercapacitor plate 178 may be connected to the common power line 172. Thedriving drain electrode 177 may be connected to the pixel electrode 710of the organic light emitting diode 70 through a contact hole.

With the above-described configuration, the switching TFT 10 may bedriven by a gate voltage applied to the gate line 151, and supply a datavoltage applied to the data line 171 to the driving TFT 20. A commonvoltage is supplied from the common power line 172 to the driving TFT20. A data voltage is supplied from the switching TFT 10. A voltagecorresponding to a difference between the common voltage and the datavoltage may be stored in the capacitor 80. A current corresponding tothe voltage stored in the capacitor 80 may flow into the organic lightemitting diode 70 through the driving TFT 20 to make the organic lightemitting diode 70 emit light.

Additionally, the flexible display 101 may further include a thin filmencapsulation layer 210 formed on the flexible substrate 111. The thinfilm encapsulation layer 210 may cover the display element 110 and abarrier film 120 disposed between the display element 110 and theflexible substrate 111.

The thin film encapsulation layer 210 may include at least one ofinorganic films 211, 213, and 215, and at least one of organic films 212and 214. In the thin film encapsulation layer 210, the inorganic films211, 213, and 215 and the organic films 212 and 214 may be alternatelystacked. The inorganic film 211 may be disposed in the lowermostportion. That is, the inorganic film 211 may be disposed closest to theorganic light emitting diode 70. FIG. 4 illustrates that the thin filmencapsulation layer 210 includes three inorganic films 211, 213, and 215and two organic films 212 and 214. However, embodiments are not limitedto this embodiment.

The inorganic films 211, 213, and 215 may be formed from at least oneinorganic material of Al₂O₃, TiO₂, ZrO, SiO₂, AlON, AlN, SiON, Si₃N₄,ZnO, and Ta₂O₅. The inorganic films 211, 213, and 215 may be formed bychemical vapor deposition or atomic layer deposition. Of these methods,the atomic layer deposition may make it possible to grow and produce theaforementioned inorganic materials at a temperature of less than 100° C.so as to prevent damage of the organic light emitting diode 70. Inaddition, the inorganic films 211, 213, and 215 formed by the atomiclayer deposition may effectively suppress permeation of moisture oroxygen because the thin films have high densities. However, embodimentsare not limited to this embodiment. The inorganic films 211, 213, and215 may be formed by various methods that are well known to those ofordinary skill in the art.

The organic films 212 and 214 may be made of polymer-based material. Thepolymer-based material may be acrylic resin, epoxy resin, polyimide,polyethylene, etc. The organic films 212 and 214 may be formed by athermal deposition process. To form the organic films 212 and 214, thethermal deposition process may be carried out in a temperature range inwhich the organic light emitting diode 70 may not be damaged. However,embodiments are not limited to this embodiment. The organic films 212and 214 may be formed by various methods that are well known to those ofordinary skill in the art.

The inorganic films 211, 213, and 215 having high thin film densitiesmay suppress permeation mainly of moisture or oxygen. The inorganicfilms 211, 213, and 215 may prevent most of moisture and oxygen frompermeating into the organic light emitting diode 70.

Moisture and oxygen passing through the inorganic films 211, 213, and215 may be blocked by the organic films 212 and 214. The organic films212 and 214 may have a relatively low ability of preventing moisturepermeation compared to the inorganic films 211, 213, and 215. However,the organic films 212 and 214 also serve as a buffer layer for reducingstress between the layers caused by the bending of the organic lightemitting display 101 between the inorganic films 211, 213, and 215 andthe inorganic films 211, 213, and 215, as well as serving to suppressmoisture permeation. That is, if the inorganic films 211, 213, and 215are consecutively formed directly on the inorganic films 211, 213, and215 without the organic films 212 and 214 interposed therebetween, whenthe organic light emitting display 101 is bent, stress is generatedbetween the inorganic films 211, 213, and 215 and the inorganic films211, 213, and 215. This stress may cause damages to the inorganic films211, 213, and 215. Consequently, the function of the thin filmencapsulation layer 210 of preventing moisture permeation may besignificantly degraded. In this way, the organic films 212 and 214 mayserve as buffer layers as well as serving to suppress moisturepermeation. Accordingly, the thin film encapsulation layer 210 maystably prevent permeation of moisture or oxygen. Also, because theorganic films 212 and 214 have planarization characteristics, theuppermost surface of the thin film encapsulation layer 210 may beplanarized.

Moreover, a thin film encapsulation layer having a thickness of lessthan 10 μm may be formed. Thus, the overall thickness of the flexibledisplay 101 may be very small.

In addition, flexibility of the flexible display 101 may be maximized byusing the thin film encapsulation layer 210.

The barrier film 120 may be formed from at least one of variousinorganic films and organic films.

The formed thin film encapsulation layer 210 and barrier film 120 maypreferably have a water vapor transmission rate (WWTR) of less than 10⁻⁶g/m²/day in order to prevent unnecessary elements from permeating intothe organic light emitting diode 70. The unnecessary elements includemoisture permeated into the organic light emitting diode 70 because suchmoisture may shorten a life span of the organic light emitting diode 70.

With the above-described configuration, the flexible display 101 mayeffectively suppress generation of a defect.

Hereinafter, a method for manufacturing the flexible display 101 asillustrated in FIG. 1 will be described with reference to FIGS. 4 to 7.

First, as illustrated in FIG. 4, a glass substrate 900 may be prepared,and then an adhesive material film 950 may be formed on the glasssubstrate 900.

The adhesive material film 950 may have the same constituents as thesurface residual film 109 of the flexible display 101 illustrated inFIG. 1. That is, the adhesive material film 950 may be made of at leastone of a metal material or a metal oxide material.

Further, the adhesive material film 950 may contain a material that maybe bonded to the functional group of —CONH—. Specifically, the adhesivematerial film 950 may contain at least one metal material including atleast one of aluminum, gallium, indium, titanium, molybdenum or zinc.The adhesive material film 950 may contain at least one metal oxidematerial including at least one of aluminum oxide, gallium oxide, zincoxide, titanium oxide, indium oxide, indium tin oxide, indium zincoxide, and gallium indium zinc oxide.

The adhesive material film 950 may be formed by sputtering, chemicalvapor deposition (CVD), or atomic layer deposition. Among these methods,the atomic layer deposition may be appropriate because the adhesive filmmaterial 950 may be formed uniformly and clearly without particles.Also, in the case of using the atomic layer deposition, the adhesivematerial film 950 may be formed to be not only uniform but alsorelatively thin. However, a deposition speed of the atomic layerdeposition is very low, i.e., approximately 0.5 Å to 2 Å per cycle.Taking these characteristics of the atomic layer deposition intoaccount, the adhesive material film 950 may be formed to have athickness t1 ranging from 0.1 nm to 1000 nm. The adhesive material film950 may be formed to be thick enough to cover the surface of the glasssubstrate 900 for surface treatment of the glass substrate 900. Thus, ifthe adhesive material film 900 is too thick, the overall productionefficiency of the flexible display 101 may be deteriorated due to arelatively low deposition speed of the atomic layer deposition. To thisend, the adhesive material film 950 may be preferably formed to have athickness t1 of less than 1000 nm.

Next, as illustrated in FIG. 5, a flexible substrate 111 may be formedon the adhesive material film 111. The flexible substrate 111 may bemade of plastic material containing the functional group of —CONH—. Inthe manufacturing method according to the embodiment, the flexiblesubstrate 111 may be formed of polyimide containing the functional groupof —CONH—. Polyimide is particularly excellent in heat resistance. Sincethe flexible display 101 has to undergo a number of high-temperatureprocesses, polyimide may be suitable as a raw material of the flexiblesubstrate 111 of the flexible display 101.

The flexible substrate 111 may be formed by either a slit coating methodor a screen printing method. That is, the polyimide may be coated on theadhesive material film 950 by the slit coating method or the screenprinting method, and the flexible substrate 111 may be formedaccordingly. At this point, the functional group of —CONH— contained inthe flexible substrate 111 may be firmly bonded to the adhesive materialfilm 950. In general, metal material or metal oxide material has verygood adhesion force to the glass substrate 900. Accordingly, theflexible substrate 111 and the glass substrate 900 may be stably adheredto each other by the adhesive material film 950.

Also, the flexible substrate 111 may be formed so as to have a thicknesst2 ranging from 5 μm to 200 μm due to a manufacturing environment or theflexible characteristics. Specifically, the flexible substrate 111having a thickness t2 of approximately 10 μm may be formed frompolyimide by the slit coating method, for example. Alternatively, theflexible substrate 111 having a thickness t2 ranging from approximately10 μm to 70 μm may be formed from polyimide by the screen printingmethod.

The flexible substrate 111 may be formed so as to have the same CTE asthe glass substrate 900 or a CTE of less than 10 ppm/° C. The glasssubstrate 900 has a CTE of approximately 4 ppm/° C. The flexiblesubstrate 111 and the glass substrate should be stably bonded to eachother. If a difference in a CTE between the flexible substrate 111 andthe glass substrate 900 becomes too large, the flexible substrate 111may be peeled off from the glass substrate 900 during a high-temperatureprocess. This may cause a defect in the manufacturing process.

Even if there is a difference in the CTE between the flexible substrate111 and the glass substrate 900, the flexible substrate 111 and theglass substrate 900 may be effectively bonded to each other, and thusenable stable manufacture of the flexible display 101.

Next, as illustrated in FIG. 6, a barrier film 120 may be formed on theflexible substrate 111, and a display element 110 may be formed on thebarrier film 120. Then, a thin film encapsulation layer 210 for coveringthe display element 110 may be formed on the flexible substrate 111.Here, the barrier film 120 and the thin film encapsulation layer 210 maybe omitted if necessary according to the type of the display element110. In addition, their configuration on the flexible substrate 111 mayvary according to the type of the display element 110.

FIG. 6 illustrates that the display element 110 is an organic lightemitting element. However, embodiments are not limited to thisembodiment. Thus, the display element may be either a liquid crystaldisplay device or an EPD device if a display device is not an organiclight emitting diode display device. Further, these display elements 110commonly include TFTs. Thus, in the manufacturing process of theflexible display 101, the flexible substrate 111 and the glass substrate900 may undergo a number of high-temperature processes, while beingbonded to each other.

Next, as illustrated in FIG. 7, a laser light L may be irradiated toseparate the flexible substrate 111 and the glass substrate 900 fromeach other. Specifically, by radiation of laser light, the flexiblesubstrate 111 and the adhesive material film 950 may be separated fromeach other, or the adhesive material film 950 and the glass substrate900 may be separated from each other.

In this manner, the flexible substrate 111 and the glass substrate 900may be separated, and the flexible display 101 may be completed. In theflexible display 101 manufactured according to the exemplary embodiment,as illustrated in FIG. 1, at least part of the metal material or metaloxide material bonded to the flexible substrate 111 may remain bonded tothe flexible substrate 111.

By the above-described method for manufacturing the flexible display101, the flexible display 101 may be stably manufactured by effectivelyimproving the bonding force between the flexible substrate 111 and theglass substrate 900.

While this disclosure has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

Exemplary embodiments have been disclosed herein, and although specificterms are employed, they are used and are to be interpreted in a genericand descriptive sense only and not for purpose of limitation.Accordingly, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made without departingfrom the spirit and scope of the invention as set forth in the followingclaims.

1. A flexible display, comprising: a flexible substrate made of plasticmaterial; a display element on a first surface of the flexiblesubstrate; and a surface residual film containing at least one of ametal material or a metal oxide material, the surface residual filmbeing bonded to at least a part of a second surface of the flexiblesubstrate, the second surface being opposed to the first surface.
 2. Theflexible display as claimed in claim 1, wherein the plastic materialincludes a functional group of —CONH—.
 3. The flexible display asclaimed in claim 2, wherein the flexible substrate is formed from amaterial containing a polyimide.
 4. The flexible display as claimed inclaim 2, wherein the flexible substrate has a thickness ranging from 5μm to 200 μm.
 5. The flexible display as claimed in claim 2, wherein theflexible substrate has a coefficient of thermal expansion ranging from 3ppm/° C. to 10 ppm/° C.
 6. The flexible display as claimed in claim 2,wherein the surface residual film contains material bonded to thefunctional group of —CONH—.
 7. The flexible display as claimed in claim6, wherein the metal material is bonded to the functional group of—CONH—, and the metal material includes at least one of aluminum,gallium, indium, titanium, molybdenum, and zinc.
 8. The flexible displayas claimed in claim 6, wherein the metal oxide material is bonded to thefunctional group of —CONH—, and the metal oxide material includes atleast one of aluminum oxide, gallium oxide, zinc oxide, titanium oxide,indium oxide, indium tin oxide, indium zinc oxide, and gallium indiumzinc oxide.
 9. The flexible display as claimed in claim 1, wherein thedisplay element includes a thin film transistor.
 10. The flexibledisplay as claimed in claim 9, wherein the display element is any one ofan organic light emitting diode display device, a liquid crystal displaydevice, or an electrophoretic display device.
 11. The flexible displayas claimed in claim 1, wherein the surface residual film has a thicknessranging from 0.1 nm to 1000 nm.
 12. A method for manufacturing aflexible display, comprising: preparing a glass substrate; formingadhesive material film on the glass substrate, the adhesive materialfilm being made of at least one of a metal material or a metal oxidematerial and forming a flexible substrate from a plastic material on theadhesive material film.
 13. The method as claimed in claim 12, whereinthe plastic material includes a functional group of —CONH—.
 14. Themethod as claimed in claim 13, wherein the flexible substrate is formedfrom a material containing polyimide.
 15. The method as claimed in claim13, wherein the flexible substrate is formed by a slit coating method ora screen printing method.
 16. The method as claimed in claim 15, whereinthe flexible substrate has a thickness ranging from 5 μm to 200 μm 17.The method as claimed in claim 13, wherein the flexible substrate hasthe same coefficient of thermal expansion as the glass substrate. 18.The method as claimed in claim 13, wherein the flexible substrate has acoefficient of thermal expansion of less than 10 ppm/° C.
 19. The methodas claimed in claim 13, wherein the adhesive material film contains amaterial capable of being bonded to the functional group of —CONH—. 20.The method as claimed in claim 19, wherein the metal material is bondedto the functional group of —CONH—, and the metal material includes atleast one of aluminum, gallium, indium, titanium, molybdenum, and zinc.21. The method as claimed in claim 19, wherein the metal oxide materialis bonded to the functional group of —CONH—, and the metal oxidematerial includes at least one of aluminum oxide, gallium oxide, zincoxide, titanium oxide, indium oxide, indium tin oxide, indium zincoxide, and gallium indium zinc oxide.
 22. The method as claimed in claim19, wherein the adhesive material film is formed by atomic layerdeposition.
 23. The method as claimed in claim 22, wherein the adhesivematerial film has a thickness ranging from 0.1 nm to 1000 nm.
 24. Themethod as claimed in claim 12, further comprising separating theflexible substrate and the glass substrate from each other.
 25. Themethod as claimed in claim 24, wherein the flexible substrate and theadhesive material film are separated from each other by radiation oflaser light.
 26. The method as claimed in claim 24, wherein the adhesivematerial film and the glass substrate are separated from each other byradiation of laser light.
 27. The method as claimed in claim 24, furthercomprising forming a display element on the flexible substrate.
 28. Themethod as claimed in claim 27, wherein the display element includes athin film transistor.
 29. The method as claimed in claim 28, wherein thedisplay element is any one of an organic light emitting diode displaydevice, a liquid crystal display device, and an electrophoretic displaydevice.